With the increasing use of optical fibre networks for multi-user Wide Area Networks (WAN) a vast amount of bandwidth is available. To take advantage of this bandwidth, a perfect shuffle network topology using wavelength division multiplexing and a multi-hop approach, has been proposed. Unfortunately, the graph connectivity of such a network is homogeneous while the communications traffic pattern for wide area networks is not. Therefore, the perfect shuffle network architecture is not suitable for WANs. The perfect shuffle network architecture, however, has been improved using a multi-dashed dual ring connected shuffle network. It has been shown that this type of network architecture can provide better performance for a WAN environment under uniform and nonuniform traffic patterns. With such a network architecture, each node has a choice of forwarding traffic on the basis of perfect shuffle network routing algorithms or ring network algorithms.
Fixed routing algorithms used in a perfect shuffle network can be effective when the traffic pattern is uniform. However, in practice, a uniform source-destination traffic pattern is unlikely in high capacity networks where there are a few nodes which generate (or sink) most of the traffic. Some nonuniform traffic patterns can cause data packets to pass through only a small subset of channels, creating overloading on such channels. In the event of a link failure between nodes on the network, a data packet may be prevented from being delivered to its destination. Efforts have been made, however, to predict traffic patterns and expected failure conditions allowing fixed routing algorithms to deal with such problems imposed by the limitations of the network.
Network conditions, such as traffic pattern and failure conditions cannot reliably be predicted in advance and, therefore, it would be desirable to make routing decisions at each node based on current network conditions. Thus, at any given instant, data packets can be routed throughout the network in the most efficient manner.